Age-related macular degeneration (AMD) is the leading cause of blindness in people over the age of 55; and diabetic retinopathy (DR) is the leading cause in people under 55 (Klein, 1994; Williams, 2004). Both diseases are characterized by new blood vessel growth—choriodal neovascularization in AMD and retinal neovascularization in DR (Freund, 1993; Speicher, 2003; Zarbin, 2004). Macular edema occurs when fluid and protein deposits collect on or under the macula of the eye (a yellow central area of the retina) and cause it to thicken and swell (edema). Diabetic macular edema (DME) is similarly caused by leaking macular capillaries. DME is the most common cause of visual loss in both proliferative and non-proliferative DR. Thrombosis of central retinal vein (CRV) and its branches is the second most prevalent vascular pathology after DR, and results in abrupt decrease in visual acuity and is accompanied by macular edema. Thus, anti-angiogenesis treatments are useful in combating all these conditions.
αv integrins have been shown to be involved in ocular angiogenesis. Expression of αv integrins is upregulated in various diseases or conditions, such as AMD and DR, and in mouse model of oxygen-induced retinopathy (OIR) or retinopathy of prematurity (ROP) model (Takagi, 2002). Also, αvβ3 is expressed in new vessels after photocoagulation, but not in normal choroidal vessels, in the laser-induced choroidal neovascularization model for AMD (Kamizuru, 2001). Administration of αv integrins antagonists, such as a cyclic RGD peptide, has been shown to inhibit retinal and choroidal neovascularization (Friedlander, 1996; Chavakis, 2002; Luna, 1996; Riecke, 2001; Yasukawa, 2004).
Angiogenesis inhibitors targeting vascular endothelial growth factor (VEGF), other growth factors (e.g., fibroblast growth factor (FGF), platelet-derived growth factor (PDGF)), chemokines (e.g., IL8, SDF1, G-CSF), receptors (e.g., CXCR1, FGF-R, PLGFR, PDGFR, Tie-receptors), intracellular mediators (e.g., c-kit kinase, PI3 kinase, PKC), and extracellular mediators (e.g., integrins, cadherins), as well as inhibitors of pro-angiogenic targets (e.g., phosphoinositide 3 kinase), have been investigated for the treatment of AMD and DR. However, application of these drugs is limited due to various concerns, such as toxicity and complexity of administration. Further, αv integrins inhibitors tested or currently in clinical trials for treating AMD and DR are not being successfully developed due to poor ocular pharmacokinetics and/or high levels of excipient/carrier (e.g., benzalconium chloride and mannitol) known to cause damage to the eye.
Thus, there continues to be a need for improved compounds, compositions, and methods for treating AMD, DR, DME, and macular edema following retinal vein occlusion, that are safe, effective, and conveniently administered. The present invention addresses the need.